A common component chemical of tires has recently been discovered as the cause of the mysterious deaths of Coho salmon.
Mysterious deaths
It has been observed for several decades how coho salmon in urban streams living in the Pacific Northwestern region have been dying.
Seattle started restoring the habitats of salmon during the 1990s and found that a maximum of 90 percent of adults that migrate into certain streams during spawning suddenly perish after the occurrence of rainstorms.
Researchers have suspected that this was caused by something which washes off roads nearby; however, they could not identify the culprit.
According to University of Washington environmental engineer Edward Kolodziej, it was a real mystery.
Kolodziei led researchers in a study published in the journal Science, which reported that the cause is a chemical that is a common component of vehicle tires meant to protect them from ozone, which is a reactive gas.
READ: Massive Amounts of Tire Particles Found Contaminating Rivers and Oceans
Chemical poisoning salmon
The toxic chemical is known as 6PPD-quinone, and it is leached out from particles that are shed by tires on roads. The research team found that even minuscule amounts are fatal for coho salmon exposed in the laboratory.
University of Toronto environmental chemist Miriam Diamond says that identifying the chemical is brilliant detective work.
READ ALSO: Researchers Confirm: Microplastics Found in Florida's Birds of Prey
Modern vehicular rubber tires
Yearly, around 3.1 billion vehicle tires are manufactured all over the world. The modern rubber tire is composed of a complicated chemical mixture, the secret formula of which is closely protected by tire manufacturers.
Tire particles are commonly found in polluted water so that scientists are interested in how such particles affect life in the water.
Determining the chemical responsible for salmon deaths
Kolodziej's research team created particle mixtures originating from nine vehicle tires. These tires were either newly bought or provided by mechanic undergraduates. The laboratory-produced mixtures were meant to mimic the particles that could be washing off from roads.
The research team found a total of several thousand chemicals that have been seen within the mixture. These were unidentified chemicals, and Zhenyu Tian, a postdoctoral student, dedicated two years to narrowing down this list by separating the different molecules depending on their various properties, including their electrical charge.
Identifying the culprit
The student already narrowed the list to approximately 50 chemicals by May 2019. After further research, the chemical of the prime suspect was finally revealed.
The formula was found to be 6PPD-quinone, a molecule produced from the reaction of 6PPD to ozone. This compound was synthesized by the research team and discovered that it was very fatal to the coho salmon in the laboratory.
The team suspected that 6PPD-quinone is found everywhere on roads with high traffic. It was found to wash off into streams from many highways such as San Francisco and Los Angeles.
Working for a solution
It might be logical to then use an alternative chemical for tires that are more environment-friendly.
According to US Tire Manufacturers Association environment, health, safety, & sustainability vice president Sarah Amick, however, more research needs to be conducted to verify and validate how this chemical in tires really cause coho salmon deaths.
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